Definition: A low pass filter is a filter that attenuates high and mid frequencies while allowing lower frequencies to pass and be heard easier. This filter is very important for simulating real world scenarios. For instance, if people are having a conversation in an adjacent room, then passing the voice work through a low pass filter would simulate the effect of hearing people through a thin wall.

Note: Keep in mind that if you want the low pass filter effect to be trigged at certain events/areas, know that such context sensitive applications require scripting--which is covered in the "Programming" section.

Select whatever audio source you wish to apply a low pass filter to.

Select Component -> Audio -> Audio Low Pass Filter. (Take note that a "Low-Pass" parameter will be added to the Listener Line Graph under 3D Sound Settings and an Audio Low Pass Filter tab will be added in the Inspector window.

Notice that there are only two properties to Audio Low Pass Filter:

Cutoff Frequency - The frequency (between 10 and 22,000 Hz) at which all higher frequencies will be cut. (For instance: putting the value at 10 means that every frequency above 10 Hz will be attenuated)

Lowpass Resonance Q (Lowpass Resonance Quality Factor) - The value (between 1.0 to 10.0) determines how much the filter's self-resonance is dampened. In other words, a high value would mean a lower rate of energy loss, so the sound's oscillations would die out more slowly.

Note: Like other parameters in the Listener Line Graph, the low pass filter can be determined based on how far the listener is from the audio source.